The present invention relates to electrical interconnection apparatus and, more specifically, to a transmission line for a load positioned in a vacuum chamber for high power, repetitively pulsed operation.
In a number of areas there is a need to interconnect an electrical load which is in a vacuum to a power supply which is not. One such area is in the creation of intense plasma sources for x-ray lithography and microwave generation. For example, in the generation of a plasma source, a transmission line is needed to supply current through a gas burst (the load) in the conversion of the electrical input to x-rays using the phenomenon of gas jet z-pinch. In this method of x-ray generation, the burst of a gas (such as nitrogen, krypton or argon) is expanded using a nozzle, in concert with the fast discharge of a capacitor bank through the expanding gas. A high current discharge generates an intense magnetic field which radially compresses the plasma. The result is a dense, high temperature plasma which is a very intense source of desirable x-rays with comparatively long wave lengths and hence poor penetrating power (commonly known as soft x-rays).
Heretofore, transmission lines used for a vacuum-enclosed load operating at high power (in excess of one gigawatt) with currents near a megampere have had limited life due to insulator failure or flashover. These lines have employed an insulator which, in effect, defined part of the vacuum chamber. When a power pulse was applied to the gaseous load, debris was generated both in gaseous and non-gaseous forms. Accretion of sufficient electrically conductive debris on the vacuum side of the insulator resulted in its electrical breakdown. For repetitively pulsed systems, operating at about 10 hertz, frequent cleaning and/or replacement of the insulator has simply not been feasible.
Various types of particle traps have been suggested for high voltage gas insulated transmission lines to keep the particles out of the insulative gas and away from high voltage conductors. For example, a particle trap could include an apertured electrode positioned adjacent an outer sheath with a deflector for directing particles to a trapping region. Or the line could be provided with an elbow joint having a relatively deep particle trap with a plurality of narrow entrance slots and inclined floor surfaces. For further information regarding the operation and structure of such prior art particle traps, reference may be made to U.S. Pat. Nos. 4,064,353, 4,034,147 and 4,029,890.